public class Test05 {
    public int peakIndexInMountainArray(int[] arr) {

        int left =  0, right = arr.length - 1;
        while(left < right){
            int mid = left + (right - left + 1) / 2;
            if(arr[mid] > arr[mid -1]) left = mid;
            else right = mid - 1;
        }
        return left;

    }
}
